Apparatus for cleaning filter screens



' June 10, 1952 J. KlNG, JR 2,599,842

APPARATUS FOR CLEANING FILTER SCREENS Filed April 18, 1951 3Sheets-Sheet l N 9 h B INVENTOR 31W J mu 3 MJWWPMAW ATTORNEY June 10,1952 Jf K N JR 2,599,842

APPARATUS FOR CLEANING FILTER SCREENS Filed April 18, 1951 3Sheets-Sheet 2 & mg wk w INVENTOR ATTORNE Y3 5 Sheets-Sheet 5 J. F.KING, JR

APPARATUS FOR CLEANING FILTER SCREENS t? INVENTOR BY j June 10, 1952Filed April 18, 1951 Patented June 10, 1952 APPARATUS FOR CLEANINGFILTER SCREENS.

James F. King, Jr.. Winston-Salem, N. 0., assignor to The BahnsonCompany, Winston- Salem, N. 0., a corporation of North CarolinaApplication April 18, 1951, Serial No. 221,601

6 Claims. (01. 183-52) The present invention relates to apparatus forcleaning; air filters and more particularly to an improved device forstripping air borne material from filter screens of the flat,reticulated type through which the air is passed for recirculation in anair conditioning system.

In textile factories particularly, a considerable mass of lint usuallybecomes entrained with the recirculating air and is caught by a filterscreen as the air passes through it. This lint must be removedperiodically if a condition of low static pressure is to be maintainedthrough the air opening across which the filter screen is placed. Onesystem of cleaning, as described in a copending' application of Agnew H.Bahnson Jr., Serial 184,316 filed September 11, 1950, now Patent No.2,596,518, granted May 13, 1952, provides. for periodic operation of ascraper blade over the face of the screen from top to bottom and. backagain. During the downward stroke, the edge of the blade is pressed intocontact with the screen surface so as to dislodge the lint and otherforeign matter. When the blade reaches the bottom of the screen, itsmotion is reversed by reversing the drive for the blade and the latterreturns to the top of the screen where its motion is again reversedthus'starting the blade downwardly again. The scraper blade is mountedon pivots and, by means of trip mechanisms at the top and bottom of thescreen, the edge of the blade is thrown into pressure contact with thescreen surface at the starting point of the downward cleaning stroke andout of contact with the screen surface at the end of such stroke. Thusduring the downward stroke the blade edge engages the screen but duringthe return, upward stroke to the starting position, the blade edge isheld away from the screen.

This application concerns the drive for the scrape blade assembly andprovides an improved arrangement for rocking the scraper blade about itspivotal support into and out of engagement with the surface of thescreen as the blade reaches the top andbottom respectively of thescreen.

The principal advantage of the improved construction about to bedescribed is that the electric motor furnishing power for driving theblade does not have to be reversed in order to reverse the direction oftravel of the blade when the latter reaches the top or bottom of thescreen. This simplifies the control in that it eliminates the necessityfor installing motor controlling limit switches which are usuallynecessary for effecting reversal of electric motor drives. More- 2 over,the improved construction provides a more positive control over thethrow of the scraper blade into and out of engagement with the surfaceof the screen.

More specifically, the present invention provides an improved, directionreversing mechanism for the scraper blade of a filter screen cleaningunit comprising a motor driven belt running in one direction only arounddiscs 10- cated at the top and bottom of the screen at one side thereof,and a crank arm, one end of the-arm being pivotally connected to a pointof attachment on the belt and the other endbeing secured fast upon arock shaft which serves as a pivotal support for the blade assembly, theshaft being journalled in vertical guides at the sides of the screen.Because of the connection between the belt and crank arm, the latterwill be compelled to travel with the connecting point on the belt thuseffecting a reciprocating movement of the rock shaft and blade assemblyin the vertical guides, the direction of which is reversedeach time thedirection of travel of the point of connection between the belt andcrank. arm is reversed as such point travels around one of the discs.The crank arm, and hence the rock shaft and blade assembly, in followingthe connection point to the belt around the disc move through an angledetermined by the diameter of thedisc thus effecting a throw of theblade assembly into surface contact with the screen as the crank armmoves around the upper disc and out of. surface contact each time thearm passes around the lower disc.

A preferred embodiment of the invention is illustrated in theaccompanying drawings as. to which Fig. 1 is a view in perspective ofthe filter screen and improved cleaner mechanism; Fig. 2 is a view invertical longitudinal section; Fig. 3 is a horizontal longitudinalsection taken on line 3-3 of Fig. 2; Fig. 4 is a fragmentary verticaltransverse section on line -A of Fig. 2 but drawn to a-larger scale;Fig. 5 is a vertical transverse section on' line 5--5 of- Fig. 6; andFig. 6 is a fragmentary vertical longitudinal section based upon Fig.2'but drawn to a larger. scale for the purpose of better illustratingconstructional detail.

With reference now to the drawings, and Figs. 1 and 2 in particular, thefilter unit is comprised of a rigid, upright rectangular frame 50 madeof metal. The bottom element of the frame is constituted by an elongatedbox 5| which serves as a receptacle for lint and other'forei gn matterremoved from the filter screen; the sidesof the frame are formed byplates 52, 53 each having a longitudinally extending channel 52a, 53a;and the top member of the frame is constituted by a flat plate 55.

The top wall |a of the box is slotted along the plane of the screen toreceive the falling lint removed by the blade, and a hinged, clean-outdoor section 5|b extending for the full length of the box is provided inthe front wall to facilitate removal of lint when the box is in need ofemptying.

The reticulated, fiat filter screen 56 is stretched taut in the frameand is secured to the latter along the top and bottom. The entire filterunit is set into filtering position which may for example be in a wallopening between two rooms. Since the present invention is directed tothe filter unit per se, it has not been considered necessary toillustrate any part of the air conditioning system with which it isassociated. However it will be understood that the air to be conditionedis blown or drawn through the filter screen 56 under pressure forcleaning. The air conditioning system may also include cooling orheating, moistening or drying components for the air but these areimmaterial to the invention.

The longitudinally extending channels 52a, 53a of the side members ofthe frame have a rectangular configuration and serve as guides forblocks or slides 51, 58 which constitute the end supports for the bladeassembly. Slides 5?, 58 are provided with horizontal bores 51a, 58arespectively which serve as bearings for rock shafts 59, 66. A singleleaf, torsion spring 6| is secured to and extends axially from the innerend of rock shaft 59 and a similar spring 62 extends axially from theinner end of rock shaft 69. Secured to the opposite ends of springs 6|,62 are axially extending shafts 63, 64, respectively which are receivedin longitudinal bores of blocks 65, 66, respectively, being lockedtherein by set screws ,61. Blocks 65, 66 are secured, as by welding, tothe under side of a plate 68 generally coextensive in width with screen56 and which projects down and inward in the direction of the screen.Extending across the bottom of this plate and secured thereto is astripper blade 69 preferably of relatively stiff rubber. During thedownward stroke, the edge of the blade is adapted to bear against thescreen at an angle of about 30 from the vertical. The included anglebetween the screen and blade edge is however not too critical and hencethe 30 angle illustrated may be departed from considerably.

To prevent undue yielding of the screen from the pressure exerted by thestripper blade 69, a backing plate 1| extends across and contacts theface of screen 56 opposite to that contacted by blade 69. Plate 1| isgenerally on the same level with blade 69 and is secured at each end tothe slidable blocks 51, 58.

While most of the lint will be pushed downward by the downward advanceof blade 69 and drop into the box 5|, some of the lint as it becomesballed or rolled up by the advancing motion of the blade maynevertheless be caught under the blade edge and left behind. To assureremoval of this remainder, there is provided a second, blade-like member12 secured to plate 68 above blade '69 extending horizontally in thedirection of but terminating just short of the screen surface. Thescraper blade 69 and the trailing blade 12 together with that portion ofplate 68 included therebetween, see Fig. 5, constitute a trap chamber'13 open in the direction of screen 56. Due to the suction of airthrough the screen, a partial vacuum is created in chamber 13 throughoutits length and such vacuum has been found most effective in trapping andbringing down any lint rolls which happen to be forced under the edge ofblade 69. The lint so trapped is discharged into box 5| when the bladeassembly reaches the end of its downward stroke and is thrown to itsout-of-contact position in a manner to be described hereinafter. Aspreviously explained, the details of the vacuum trap chamber are claimedin the other, copending application of Agnew H. Bahnson, Jr., Serial No.184,316.

For advancing the blade assembly downwardly across the face of thefilter screen, a flexible, endless belt type of drive, preferably of thepositive chain and sprocket type, is utilized at each end of the bladeassembly. Thus as most clearly seen in Fig. 2, a geared down electricmotor 14 supported upon bracket 15 attached to the left side of thescreen frame 50 drives sprockets 16, 11 at the upper left side of theframe. Sprocket TI is connected by chain 18 to another sprocket 19located at the lower, left side of the frame and which is mounted upon ashaft journalled in sleeve bearing block 800.. Sprocket I6 is connectedby another chain 8| to another sprocket 82 located above it and which issecured fast upon a shaft 83 extending transversely of frame 59 andjournalled at its ends in sleeve bearing blocks 84, 85. A sprocket 86secured fast on the opposite end of shaft 83 is connected by chain 81 toa sprocket 88 secured fast upon a stub shaft 89 journalled in sleevebearing block 90 at the same level as the shaft of motor 14. Anothersprocket 9| fast upon shaft 99 is connected via chain 92 with anothersprocket 93 mounted upon shaft 94 rotatable in sleeve bearing 94alocated at the lower right corner of the screen frame at the same levelas sprocket 19. Thus when motor I4 is energized, it will drive chain 18at the left side of the frame directly. The correspondingly positionedchain 92 at the right side of the frame will be driven indirectlythrough the auxiliary sprocket and chain connections described, and inthe same direction as chain 18.

As more clearly seen in Figs. 3 and 4, the respective axes of rotationof the four sprockets l1, 19, 9| and 93 are located in a common verticalplane coincident with the aligned axes of the two rock shafts 59 and 69.Hence each of the chain belts I8 and 92 will occupy a vertical planeextending transversely of the aligned axes of the two rock shafts 59,60. A crank arm 95 is secured fast upon rock shaft 59 at one end, andthe other end of the arm is pivotally connected at 96 to one link onchain 18. In a similar manner, another crank arm 91 has one end securedfast upon rock shaft 69 and the other end pivotally connected at 98 to alink on chain 92, it being noted that the pivotal connections 96, 98 lieon the same flight of the chains and at like levels. Movement of chains18 and 92 in the direction indicated on Fig. 4 cause the blade assemblyto be carried downwardly with the blade 69 pressed against the surfaceof screen 56, the downward pull being exerted from the chains throughpivotal connections 96, 98 and from the latter via crank arms 95, 91,rock shafts 59, 69, and torsion springs 6|, 62 to the blade assemblyconsisting of plate 68 and the two blades 69, 72.

When the pivotal connections 96, 98 reach the bottom, pass around thelower sprockets Hi, 93 andstart upward, it will be" evident" that crankarms 95'; 91 will be thrown from thlefti'to: the right side of theplanethrough the centers of the-"four sprockets 1T,"-19-, 9| and '93viewed from the left in Fig; '2, i; e.'=as in Fi '4, thus throwing"rockshafts'59, 60 counterclockwise-to the other position shownin' brokenlines in 4 wherein the stripper blade is out of contact with the screensurface and reversing the directionof motionof the blade assembly;'Whe'n the pivotal connections 95, fli'reachthe top and passaround theupper sprockets"'l'1and 9|, crank-arms'95, 91 are thrown back to theleft side of the plane throughthe sprocket centers to the position shownin fulllines in Fig. 4 thus again reversing the direction of "travel ofthe bladeassembly and ain throwing the blade 69 into contact. with thesurface of the filter screen'for the downward clean -off stroke. Theangular relationship between crank arms'Q-S, 91 and-blade is such thatthe edge of blade 69 will contact the screen when the crank arms 95, 91have moved through approximately two thirds of their angle of throw as"the pivotal connections 95-, 98 travel from one side to the other of theupper sprockets I1 and SI. The remaining one thirdof the angular throwof crank arms 95; 91 is used to load the torsion springs El, 62 thusassuring a firmpressure of the edge of blade 69 against screen 55 duringthe downward stroke. The load of springs SI, 62 against the blade 69 isabsorbed by the backing plate H which as previously explained travelswith the cleaning blade.

Cleaning of the filter screen can be made selective at the will of theuser in which suitable control switches would be included in the circuitof motor 14 to connect the latter to a source of power whenever thescreen was deemed in need for cleaning. Or, operation of the cleanercould be made automatic in which case suitable timer mechanism would beincorporated in the control circuit of the motor to effect energizationthereof at selected intervals fora selected period of operation in eachinterval.

In conclusion it will be understood that the particular embodiment of myinvention hereinabove described is but typical of the many structuralarrangements possible and hence various modifications thereof may beeffected without however departing from the spirit and scope of theappended claims.

Accordingly, what I claim as new and desire to secure by Letters Patentof the United States 15:

1. Apparatus for stripping lint and like material from a flat filterscreen through which air is adapted to be passed comprising a framehaving said filter screen secured thereto, said frame including a pairof side members provided with longitudinally extending guides, a slidedisposed in each guide, a wiper blade for the screen extendingtransversely of said frame, means supporting said blade on said slidesfor rocking movement about an axis extending longitudinally ofthe bladeto bring the blade edge into or out of contact with the surface of saidscreen, a flexible drive at one side of said frame for said blade, saiddrive including a belt occupying a vertical plane extending transverselyof the support axis for said blade and running on rotatable discsdisposed respectively at opposite ends of said frame, a crank arm havingone end thereof pivotally attached to a connection point on said belt,means for driving said belt and means interconnecting the other endof'said crank arm"with said blade supporting means such that the throwof the cran'k-- arm effected each time the pivoted "end 'of' thelatterpasse's around one of said discs isconverted into a rockingmovement'of said blade. T

2, Apparatus for stripping lint and like material from afiat'filter'screen through which'air isadapted to be passed comprising avertical a'crank'arm extending from said} rock shaft means, meanspivotally' connecting the outer end of said crank arm to said belt, andmeans for driving said "belt to'th'ereby effect reciprocation of saidslides and hence also said rock shaft means and blade, said rock shaftmeans being thrown from one position to the-other by-the throw of saidcrank arm each time the pivotally connected end of the latter passesaround each of said discs to thereby throw said blade into and out ofcontact, respectively with the surface of said filter screen.

3. Apparatus for stripping lint-like material from a filter screen asdefined in claim 2 wherein the means securing said wiper blade to saidrock shaft means includes spring means extending therebetween forloading the edge of said blade against the screen surface.

4. Apparatus for stripping lint and like material from a fiat filterscreen through which air is adapted to be passed under pressurecomprising a vertical frame having said filter screen attached thereto,said frame including a pair of side members provided with longitudinallyextending guides, a slide disposed in each guide, coaxial horizontalrock shafts carried respectively by said slides, a wiper blade at theair intake side of said screen carried by and secured to said rockshafts for rocking movement with the latter to bring the blade edge intoor out of contact with the surface of said screen, a flexible drive ateach side of said frame for the associated slide, each side driveincluding a belt occupying a vertical plane extending transversely tothe axis of said rock shafts extending longitudinally of said frame andrunning on rotatable discs disposed respectively at the top and bottomof said frame and a crank arm having one end pivotally attached to aconnection point on said belt and the opposite end secured fast upon theassociated rock shaft, and means for driving said belts to thereby causesaid slides to be reciprocated in said guides and effect reciprocationof said rock shafts and blade across the face of said screen, said rockshafts and blade being thrown from one position to the other by thethrow of said crank arm each time the pivoted end of the latter passesaround on of said discs.

5. Apparatus for stripping lint and like material from a flat filterscreen through which air is adapted to be passed comprising a verticalframe having said filter screen secured there- 7 to, said frameincluding frame members at each side thereof provided withlongitudinally extending guides, a slide disposed in each guide, rockshaft means journalled in said slides and extending transversely of saidframe, a wiper blade extending between said slides and supported uponsaid rock shaft means, a flexible drive at each side of said frame, eachsaid drive including a belt occupying a vertical plane extendingtransversely of the axis of said rock shaft means and running onrotatable discs disposed respectively at the top and bottom of saidframe, the axes of said discs occupying a vertical plane containing theaxis of said rock shaft means and a crank arm, means pivotallyconnecting one end of each said crank armrto correspondingly locatedpoints on said belts, the other ends of said crank arms being securedfast upon opposite ends of said rock shaft means, and means for drivingsaid belts in the same direction and at like speeds to thereby causesaid slides to be reciprocated in said guides and effect reciprocationof said rock shaft means and wiper blade across the face of said screen,said rock shaft means and blade being moved by the throw of said crankarms to eifect engagement between the blade edge and screen each timethe pivotally connected ends of said crank arms pass around the discs atthe top of 8 said frame and to disengage the blade edge from said screeneach time the pivotally connected ends of said crank arms pass aroundthe discs at the bottom of said frame.

6. Apparatus for stripping lint-like material from a filter screen asdefined in claim 5 and which further includes torsion spring meansintermediate said wiper blade and rock shaft means, said wiper bladebeing carried by said spring means and adapted to be loaded by thelatter into pressure contact with the surface of said screen as saidcrank arms are thrown to the blade engaging position.

JANIES F. KING, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Germany Jan. 23, 1913

